/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
╞══════════════════════════════════════════════════════════════════════════════╡
│ This is free and unencumbered software released into the public domain.      │
│                                                                              │
│ Anyone is free to copy, modify, publish, use, compile, sell, or              │
│ distribute this software, either in source code form or as a compiled        │
│ binary, for any purpose, commercial or non-commercial, and by any            │
│ means.                                                                       │
│                                                                              │
│ In jurisdictions that recognize copyright laws, the author or authors        │
│ of this software dedicate any and all copyright interest in the              │
│ software to the public domain. We make this dedication for the benefit       │
│ of the public at large and to the detriment of our heirs and                 │
│ successors. We intend this dedication to be an overt act of                  │
│ relinquishment in perpetuity of all present and future rights to this        │
│ software under copyright law.                                                │
│                                                                              │
│ THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,              │
│ EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF           │
│ MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.       │
│ IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR            │
│ OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,        │
│ ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR        │
│ OTHER DEALINGS IN THE SOFTWARE.                                              │
│                                                                              │
╚─────────────────────────────────────────────────────────────────────────────*/
#include "libc/dns/servicestxt.h"

#include "libc/bits/safemacros.internal.h"
#include "libc/dce.h"
#include "libc/errno.h"
#include "libc/fmt/conv.h"
#include "libc/fmt/fmt.h"
#include "libc/macros.internal.h"
#include "libc/mem/mem.h"
#include "libc/nt/systeminfo.h"
#include "libc/runtime/runtime.h"
#include "libc/str/str.h"

static textwindows noinline char *GetNtServicesTxtPath(char *pathbuf,
                                                       uint32_t size) {
  const char *const kWinHostsPath = "\\drivers\\etc\\services";
  uint32_t len = GetSystemDirectoryA(&pathbuf[0], size);
  if (len && len + strlen(kWinHostsPath) + 1 < size) {
    if (pathbuf[len] == '\\') pathbuf[len--] = '\0';
    memcpy(&pathbuf[len], kWinHostsPath, strlen(kWinHostsPath) + 1);
    return &pathbuf[0];
  } else {
    return NULL;
  }
}

/**
 * Opens and searches /etc/services to find name for a given port.
 *
 * format of /etc/services is like this:
 *
 *      # comment
 *      # NAME      PORT/PROTOCOL   ALIASES
 *
 *      ftp		    21/tcp
 *      fsp		    21/udp		    fspd
 *      ssh		    22/tcp
 *
 * @param servport is the port number (in network byte order)
 * @param servproto is a pointer to a string (*servproto can be NULL)
 * @param buf is a buffer to store the resulting name
 * @param bufsize is the size of buf
 * @returns 0 on success, -1 on error
 *
 * @note aliases are not read from the file.
 */
int LookupServicesByPort(const int servport, char **servproto, char *buf,
                         size_t bufsize) {
  FILE *f;
  char *line;
  char pathbuf[PATH_MAX];
  const char *path;
  size_t linesize;
  int count, found;
  char *name, *port, *proto, *comment, *tok;

  path = "/etc/services";
  if (IsWindows()) {
    path = firstnonnull(GetNtServicesTxtPath(pathbuf, ARRAYLEN(pathbuf)), path);
  }
  if (bufsize == 0 || !(f = fopen(path, "r"))) {
    return -1;
  }
  line = NULL;
  linesize = 0;
  count = 0;
  found = 0;

  while (found == 0 && (getline(&line, &linesize, f)) != -1) {
    if ((comment = strchr(line, '#'))) *comment = '\0';
    name = strtok_r(line, " \t\r\n\v", &tok);
    port = strtok_r(NULL, "/ \t\r\n\v", &tok);
    if (name && port && servport == htons(atoi(port))) {
      if (!(proto = strtok_r(NULL, " \t\r\n\v", &tok)))
        continue;
      else if (!servproto[0]) {
        servproto[0] = strdup(proto);
        strncpy(buf, name, bufsize);
        found = 1;
      } else if (strcmp(proto, servproto[0]) == 0) {
        strncpy(buf, name, bufsize);
        found = 1;
      }
    }
    count++;
  }
  free(line);

  if (ferror(f)) {
    errno = ferror(f);
    return -1;
  }
  fclose(f);

  if (!found) return -1;

  return 0;
}

/**
 * Opens and searches /etc/services to find port for a given name.
 *
 * @param servname is a NULL-terminated string
 * @param servproto is a pointer to a string (*servproto can be NULL)
 * @returns -1 on error, or
 *          positive port number (in network byte order)
 *
 * @note aliases are not read from the file.
 * @see LookupServicesByPort
 */
int LookupServicesByName(const char *servname, char **servproto) {
  FILE *f;
  char *line;
  char pathbuf[PATH_MAX];
  const char *path;
  size_t linesize;
  int count, found, result;
  char *name, *port, *proto, *comment, *tok;

  path = "/etc/services";

  if (IsWindows()) {
    path = firstnonnull(GetNtServicesTxtPath(pathbuf, ARRAYLEN(pathbuf)), path);
  }
  if (!(f = fopen(path, "r"))) {
    return -1;
  }
  line = NULL;
  linesize = 0;
  count = 0;
  found = 0;
  result = -1;

  while (found == 0 && (getline(&line, &linesize, f)) != -1) {
    if ((comment = strchr(line, '#'))) *comment = '\0';
    name = strtok_r(line, " \t\r\n\v", &tok);
    port = strtok_r(NULL, "/ \t\r\n\v", &tok);
    if (name && port && strcmp(name, servname) == 0) {
      if (!(proto = strtok_r(NULL, " \t\r\n\v", &tok)))
        continue;
      else if (!servproto[0]) {
        servproto[0] = strdup(proto);
        result = htons(atoi(port));
        found = 1;
      } else if (strcmp(proto, servproto[0]) == 0) {
        result = htons(atoi(port));
        found = 1;
      }
    }
    count++;
  }
  free(line);

  if (ferror(f)) {
    errno = ferror(f);
    return -1;
  }
  fclose(f);

  if (!found) return -1;

  return result;
}